Method of manufacturing printed circuits

ABSTRACT

A process and apparatus for producing supported conductive networks which can be flexible or rigid, having densely packed circuits. The process and apparatus for making the conductive network involves forming a conductive material supported on a &#34;dynamic pressure cushion&#34; into a non-planar pattern defining the desired conductive circuits in relation to a fixed reference plane. The &#34;dynamic pressure cushion&#34; is a material having suitable viscosity and flow characteristics to flow out from under the conductive material as it is being formed and fill up any voids. To ensure that the &#34;dynamic pressure cushion&#34; properly flows without deforming the desired circuits, the die used to form the conductive material is provided with a material flow control grid and material expansion troughs. After forming the unwanted material is then mechanically removed in dimensional relation to the reference plane leaving the desired conductive circuits.

This application is a Continuation-in-Part of U.S. patent applicationSer. No. 08/016,002 filed Feb. 10, 1993 (now U.S. Pat. No. 5,477,612)which is in turn a Continuation-in-Part of U.S. patent application Ser.No. 07/837,357 filed Feb. 14, 1992 (now U.S. Pat. No. 5,343,616).

FIELD OF THE INVENTION

This invention generally relates to an environmentally desirable methodfor producing high density electrically conductive networks supported bya layer of flexible or rigid dielectric, which have densely packedconductive paths, the supported networks themselves and associatedapparatus.

1. Definitions

The term "Conductor" as used herein shall be construed to be anelectrical conductor.

The term "Reference plane" as used throughout the specification andclaims is intended to include planar, cylindrical (i.e. a roller) andany other single curvature surface appropriate to a given manufacturingsituation as well as the preferred planar surface.

The term "die" as used herein includes planar, cylindrical, or curveddies that cooperate with a planar, cylindrical, or single curved supportsurface arranged to provide support at the reference plane.

The term "Dynamic Pressure Cushion" is used herein to describe thecharacteristics of an adhesive, dielectric and/or compliant carrier usedto support a conductive foil during formation of a conductive network ofthe invention. The dynamic pressure cushion has a viscosity duringforming which is fluid enough to allow the carrier to flow out fromunder depressed circuit forming portions of the foil and to fill allvoids under the foil while being viscous enough to support and evenraise the waste material to a prescribed level for waste removal.

The term "Control Grid" as used herein refers to features of the diearranged, positioned and dimensioned to control movement of the carrierduring formation of a conductive network of the invention.

The term "parallel" as used herein shall be construed to include"coincident with" e.g. a plane coincident with a surface of a lamina.

The term "thin" as used herein shall be construed to define a layer ofmetallic or dielectric material having a thickness of less than 0.13 mm(0.005"), preferably in the range of 0.018 mm (0.0007") to 0.11 mm(0.0042").

2. Background of the Invention

One class of supported networks to which the present invention relatesis frequently characterized by the term "printed circuits." (The term"circuit" will be used to signify one or more conductors, combinationsthereof, electrical, including magnetic components per se, or suchcomponents and associated conductors.) The term "printed circuits"originates from the technique of printing the electrical assembly, whichmay comprise, for example, a network of conductors, the stator of aswitch or the rotor of a motor, on an insulated base by means of theselective deposition of a conductive material thereon in conformity withthe desired circuit configuration. Electrolytic, electroless andmechanical (spraying, sputtering, etc.) techniques have been employed toprovide this printing operation.

In addition to the above, the term "printed circuits" has been appliedto components, assemblies or circuits formed by techniques ofselectively removing sections from an insulation-backed conductiveblank, by selectively etching the non-conductive regions, the conductivecomponents being protected by an etch resist printed on the blank inconformity with the desired circuit configuration.

In addition to the production of printed circuits, the methods of theinvention are applicable to the production of other electricalcomponents heretofore produced by solely mechanical means such as bystamping.

Burdening all of the foregoing techniques are certain limitations. Manyof the techniques are not sufficiently accurate, require expensivemachinery and are frequently impractical where a design is to be mountedon or laminated to an insulated base. The usual printed circuittechniques are environmentally undesirable and incompatible with therequirements for mass production, needing elaborate environmentalcontrol, having a susceptibility to latent defects in the resultantproduct (and thus requiring rigorous quality control), and beingrelatively expensive. Frequently it is necessary to provide temporarysupports during various production stages. Moreover, the strength ofmany printed circuits leaves much to be desired. Generally, onlyrelatively thin, flat structures can be produced. This, together withhigh resistivity and tendencies to delaminate and deteriorate undercertain conditions have limited the applicability of these circuits. Inspite of this, the trend is toward wider adoption of printed circuittechniques, this being due in part to the increasing emphasis on weightreduction and miniaturization and to the prohibitive costs in time,labor and materials of conventional circuit wiring and cablingprocedures.

Developments in the electronics industry require the use of more denselypacked electrical modules and circuits, each requiring multipleinterconnections to one another. However, there is a practical limit tothe density that can be achieved using conventional conductive networks.In a typical present day application, a floppy disk drive may require aconnection to a recording head whose conductors are only on the order of0.2 mm (0.008 inches) on center and associated jumper conductors musthave a similar spacing. Further, recent liquid crystal displays haveconductors which are even more closely packed, for example, 0.1 mm(0.004 inches) on center, with similar requirements for interconnectionconductors. In addition, there is growing use of ceramic PC boards toaccommodate multiple IC chip arrays which also require high densityconnectors and custom interconnect cables for purposes of terminatingthose components.

As a direct result of the growth in the circuit board industry, therehas been a parallel increase in the volume of environmentally-hazardouschemicals generated by the conventional etching and depositionprocesses. For example, it is not uncommon for one circuit boardfabrication facility to generate 4,000 liters (1,000 U.S. gallons) perday of photo resist stripper and 4,800 liters (1,200 U.S. gallons) perweek of developer solution. These toxic wastes must be transportedoff-site for proper disposal at hazardous waste management sites. Thus,there is an urgent need for a practical non-chemical method for themanufacture of conductive networks, particularly high density conductivenetworks.

It is known to form a planar electrically conductive sheet into anon-planar pattern in a purely mechanical process, i.e. no etching isinvolved, by forming a conductive foil to define a circuit patternspaced by waste material, the foil being attached to a dielectricmaterial before, during or after forming, and surface machining thewaste material off. However, the known methods of mechanically formingcircuits have never been able to attain commercial acceptance due totechnical problems and are unable to produce the high density networksrequired by modern technology.

One significant technical problem, ignored by the prior art, is whathappens to the adhesive or dielectric when forming a planar electricallyconductive sheet into a non-planar pattern. The known prior art suggeststhat the adhesive and/or dielectric is compressed into a smaller space.This is both dimensionally impractical and extremely unstable, as itbuilds compression stresses into the structure. As the waste material ismachined off, the compressed material expands changing the location ofconductors in the X, Y and Z planes thereby altering the desired circuitpattern, perhaps even causing portions of the desired circuits to beremoved. This condition virtually eliminates any possibility ofaccomplishing the precision machining required to create fine lineconductors in a high density network circuit. All known prior artignores one or more of the following fundamental technical problems thathave prevented these known processes from achieving any degree ofcommercial success. Current art does not teach us how to:

1. Form a sheet of conductive material as thin as or thinner than 0.02mm (0.0007") thick sheet of conductive material into a non-planarpattern and protect its formed shape as it is processed throughlamination and machining operations without damaging the formedstructure;

2. Form a laminate, consisting of a conductive material attached to adielectric, while maintaining the flatness and precise location ofconductors within the structure as is necessary to successfully removeall waste and maintain the desired conductor thickness;

3. Form a laminate, consisting of a conductive material attached to adielectric, while maintaining a substantially flat and stable referenceplane necessary for precise location of conductors within the structureand for precise removal of waste material.

4. Eliminate the distortion, resulting from compression stresses, thatoccurs as waste material flows away from the embossed pattern. NOTE:Material must be undistorted for the accurate grinding of waste materialoff;

5. Stabilize, support and entrap a thin conductor (e.g. 0.02 mm(0.0007") thick and 0.025 mm (0.001") wide), to prevent its movement ordelamination, as the waste material is mechanically ground off;

6. Emboss a conductive foil into an adhesive layer less than half itsthickness. (e.g. Embossing a 0.04 mm (0.0014") thick conductive foil(circuit pattern) into an adhesive layer less than 0.02 mm (0.0007")thick and surface machining off the waste material off leaving a 0.04 mm(0.0014") thick conductor;

7. Create a finished circuit with a variety of conductor thicknessesdesigned to accommodate specific electrical and/or mechanicalrequirements;

8. Eliminate the technical and cost limitations related to preparing andapplying a dielectric overlay;

9. Attach a temporary carrier that is generally a "compliant material"and as such can be conditioned (heat and/or pressure) to assists infirst forming a structure (either a laminate consisting of a conductivematerial attached to a dielectric or conductive material) and onceformed, maintaining that structure's critical dimensions (flatness ofthe temporary carrier necessary to establish and maintain a truemachining reference plane based on the location of the conductors andthe desired conductor thickness) necessary to successfully remove allwaste material and maintain the desired conductor thickness.

Due to the technical problems experienced by the prior art techniquesthey are unable to mass produce high density, multiple fine line circuitnetworks. The known techniques are limited to relatively thick, lowdensity circuits and are therefore unsuited to meet today's demand forhigh density, fine line conductive circuits, for example multipleconductors spaced at 0.1 mm (0.004") on center.

It is a primary object of the present invention to provide a method ofmanufacturing a relatively inexpensive, high-quality, densely packed,supported conductive network for use in fabricating rigid or flexiblecircuit boards, without the use or generation of environmentallyhazardous chemicals.

Other objects of the invention are to overcome shortcomings of the priorart as set forth in the numbered sub-paragraphs above and, inparticular, to provide a method of forming a planar conductive materialinto a non-planar pattern either independently or when attached to adielectric, in which:

a) the formed conductors may be positioned in spaced relationship toeach other and to a fixed reference plane, defined by, for example, thedielectric, to ensure proper waste removal and conductor shaping,thickness, width and configuration);

b) a conditioned adhesive and/or dielectric is used to receive, captureand support a formed conductor pattern and to eliminate half of a dieset (either the male, when extruding a conductive material or a femalewhen forming a foil/dielectric laminate);

c) each individual conductor is supported on at least three of its foursides, through the lamination and machining operations to ensure thatthe conductors are not separated from the dielectric;

d) a flexible conductive network forms conductive paths which areprofiled to self-align with corresponding conductors of other conductivenetworks;

e) a thin sheet of conductive material is formed into a non-planarpattern and processed without damaging the formed structure;

f) the flatness and precision, of a laminate, necessary to remove wasteand maintain the desired conductor thickness is accurately maintained;

g) distortion problems that occur during the forming operations in theprior art are eliminated;

h) a method able to stabilize, support and entrap a thin conductor toprevent delamination as the waste material is ground off is provided;

i) a conductive foil is embossed into an adhesive layer less than halfit's thickness.

SUMMARY OF THE INVENTION

Simply stated the method of the present invention relies on four basicprinciples for creating a conductive circuit pattern, namely:

1) Forming, a planar conductive material into a non-planar patterndefining a desired circuit pattern;

2) Positioning the formed conductors in a fixed spaced relationship toeach other and to a reference plane, such as the planar exposed surfaceof a dielectric fast with the formed foil. This "reference plane" iscritical to proper waste removal and conductor shaping (thickness, widthand configuration) in high density conductive networks;

3) Providing an adhesive and/or dielectric having a characteristicssuitable to receive, capture and support a formed conductor pattern andcontrolling its flow during the forming operation. Use of an adhesiveand/or dielectric in a state having the correct viscosity allows theelimination of half of a die set (either the male half when extruding aconductive material or the female half when forming a laminate); and

4) Supporting each individual conductor, on at least three of its foursides, through the lamination and grinding operations. This supportensures that the conductors do not separate from the dielectric.

According to the invention there is provided a method for manufacturinga network of electrically conductive paths supported by a dielectricmaterial comprising the steps of a) providing a conductive metalliclamina; b) supporting the lamina on a first surface thereof; c) defininga reference plane positioned parallel to the lamina; d) mechanicallyforming the lamina into a non-planar pattern defining the network ofconductive paths substantially parallel to the reference plane; and e)machining the lamina, parallel to the reference plane, along a boundarybetween waste material of the lamina and the network of conductivepaths, to remove the waste material and leave the network of conductivepaths; a layer of dielectric material being made fast with the lamina,before step e), such that the conductive paths are supported throughoutperformance of the method.

Unlike some conventional techniques for fabricating conductive networks(for example, etching and deposition), the process of this inventiondoes not use etchant, environmentally-hazardous resist, stripper, anddeveloper solutions. Thus, the expense and environmental hazardsassociated with having the resist, stripper and developer wastesolutions transported to toxic waste management sites is eliminated.Further, the process of this invention eliminates common yield problemsassociated with conventional etched circuits, e.g. art work distortion,scratched or bad acid resistant ink, inconsistent etching caused bydirt, dust or impurities in the material being etched, and questionableetching chemistry. Thus, the use of this process will result in asignificant reduction in labor costs and an increase in product yield.

This process offers other significant advantages over the conventionalimaging and etching or additive (plating-up) techniques normally used tomake printed circuit conductive networks. For example, it allows the useof relatively low cost, relatively inferior metal sheets or foils withminor inclusions, impurities or voids which cannot be used in a processinvolving etching because this would result in non-uniform etch rates.Materials that cost as little as half as much as those required foretching may be used in the present process without any detrimentaleffects on the process or on the final product. Further, in the processof this invention, the throughput is the same for circuits whose metalfoils have different thicknesses. This contrasts to the usualimaging-etching process wherein the line speed is directly proportionalto the foil weight because it takes longer to etch thick foil than thinfoil. The following is intended to summarize the versatility andtechnical advantages of the inventive process:

a) Elimination of hazardous chemical processing materials and relateddisposal expenses;

b) Once the electrical and mechanical characteristics of a circuit areestablished and built into the hardened steel template, there is circuitrepeatability;

c) Equal effectiveness on high volume and intermediate volume jobs;

d) Base laminate may be fused (melted) to the formed conductive sheeteliminating the need for an adhesive (This can only be accomplished,without causing conductor distortion (swim), using the inventiveprocess);

e) Elimination of common yield problems associated with conventionaletched circuits such as, artwork distortion, dirt or dust, scratchedresist, inconsistent etching chemistry, etc;

f) A significant reduction in direct labor costs;

g) Conductors can be plated with any surface finish;

h) The ability to produce a conventional copper circuit for less than1/2 of direct manufacturing costs using etching techniques;

i) The ability to manufacture low cost, channelled conductors insulatedwith any flexible or rigid insulating material;

j) The ability to manufacture low cost, channelled conductors insulatedand mounted to a second circuit network and/or to a support spring orcomponent stiffener; and

k) The ability to make high-density contact clusters for connectorassemblies.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example, with referenceto the accompanying drawings, in which:

FIG. 1 is a plan view and FIG. 2 is a cross-sectional view, taken alongline 2--2 in FIG. 1, of a portion of a circuit used to illustrate theformation of that circuit, out of a thin sheet of electricallyconductive material, according to the invention;

FIG. 3 is a cross-sectional view of a portion of a forming die used inthe invention;

FIGS. 4-7 illustrate a method according to a first embodiment of theinvention for forming a circuit from a thin sheet of conductive materialsupported on a dielectric;

FIGS. 8-13 illustrate a method according to a second embodiment of theinvention for forming a circuit from a thin sheet of conductive materialsupported on a temporary compliant carrier;

FIG. 14 is a plan view, FIG. 15 is a cross-sectional view, taken alongline 15--15 in FIG. 14 and FIG. 16 is a cross-sectional view taken alongline 16--16 in FIG. 14, showing a portion of a circuit for illustratingembodiments of the invention in which a layer of conductive material isextruded into a non-planar pattern;

FIGS. 17-22 illustrate a third embodiment of the invention for forming aconductive circuit in which a layer of conductive material is extrudedto form a non-planar pattern and preformed dielectric is placed thereon;

FIGS. 23-27 illustrate a fourth embodiment of the invention for forminga conductive circuit pattern in which a layer of conductive material isextruded to form a non-planar pattern and an unformed dielectric isapplied thereto;

FIGS. 28-33 illustrate a method according to a fifth embodiment of theinvention for forming ultra thin conductive circuits in which theconductive circuit is formed by extrusion and then machined from bothsides thereof;

FIG. 34 illustrates a portion of a circuit produced in accordance withthe present invention showing various features of the circuit; and

FIGS. 35-37 illustrate a method according to a sixth embodiment of theinvention for simultaneously producing multiple layers of conductivecircuits separated by an intermediate layer(s) of dielectric.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Referring to FIGS. 1 and 2, a flexible conductive network incorporatingthe invention is shown generally at 1. The network has a dielectricsubstrate 2 which carries densely packed conductive paths 3. Eachconductive path 3 has a bottom wall 3a and a pair of spaced-apartinclined side walls 3b so that the cross-section of each conductive path3 is trough-like. The bottom wall 3a is generally recessed from about0.025 mm (0.001 inches) to about 0.127 mm (0.005 inches) below thesurface of the conductive network.

Although conductive paths 3 depicted in FIGS. 1 and 2 are shown as beingstraight and parallel to one another, the conductive paths may havevarious patterns and follow different paths along substrate 2, orinterconnect, provide contact pads and many other circuit features,depending upon the particular network application, by appropriatelycontrolling the forming operation described below.

Embodiment 1: Forming A Conductive Network From A Thin Conductive SheetSupported On A Dielectric

Referring now to FIGS. 3 to 7, in the method according to the firstembodiment of the invention, a desired circuit pattern with conductivepaths 3 properly positioned in relationship to a reference plane 4 andsupported by a dielectric 2 laminated to the conductor by an adhesive 5(also a dielectric), is produced by the following steps.

Step a:

A forming die 6 (FIG. 3) is provided that has a forming surface 7 withshaped features thereon for forming a conductive foil 8 (FIG. 4) into anon-planar pattern defining the final conductive circuits 3. The die 6also has shaped features for controlling the flow of adhesive 5underlying the conductive foil 8 during forming to accommodate materialexpansion and/or displacement and achieve a machinable surface.

The shaped features on the die 6 include raised circuit forming elements9 to depress the conductive foil 8 into the adhesive 5 to form circuitfeatures (FIG. 5), in the conductive foil 8, that define the desiredconductive paths 3. By varying the width and height of the circuitforming elements 9, respectively, a variety of conductive path widthsand thicknesses may be produced in the final circuit pattern.

Material displacement control grid features 10 are also provided on thedie to depress the conductive foil 8 to capture and control the flow ofadhesive 5 during forming. Moreover, the die 6 defines materialexpansion troughs 11 that allow the conductive material to be displacedupwards during forming (FIG. 5), thereby relieving compression stressesthat would otherwise distort the circuit during machining. It iscritical for accurate waste material removal that the adhesive 5 isdisplaced during forming and not compressed. The expansion troughs andcontrol grid features are designed to stabilize the formed structurewhile maintaining a machinable surface parallel to the reference plane4. The reference plane 4 is defined by a planar surface of thedielectric 2 remote from the conductive foil 8.

Precision die stops 12, designed to accurately control the location ofeach conductor in relationship to the reference plane 4, are provided onthe die 6. The die stops 12 accurately control the die relative to thereference plane 4.

Step. b:

A laminate 13 is provided, (FIG. 4) consisting of a planar conductivemetallic foil 8 (e.g., copper) of a suitable thickness, for example,about 0.04 mm (0.0014") and a flexible dielectric material 2, forexample, 0.05 mm (0.002") thick Kapton sheet, is provided. Thedielectric 2 is adhered to the conductive foil 8 by a layer 5 ofdielectric adhesive material, for example, 0.12 mm (0.004") thick. Ifdesired the foil may be plated as indicated by numeral 14.

The adhesive 5 is selected or conditioned using heat, pressure and/orformula modification, to have a viscosity that supplies a flowablecompliant dynamic pressure cushion, i.e. it supports the conductivesheet throughout the process while flowing out from under the conductivefeatures and filling all voids. To maintain the required dimensionalrelationship of the conductive foil relative to the reference plane 4during waste removal, it is critical that the adhesive 5 flows out fromunder the depressed portions of the conductive foil 8 during formingwithout being compressed, thereby relieving compression stresses thatare otherwise formed, and completely fills the spaces 16 between thecircuit features to support the circuit features on three sides.Supporting the circuit features on three sides serves to stabilize,support and entrap the circuit features preventing their movement ordelamination in subsequent processes. The quantity and fluidity ofadhesive is controlled so that it suitably flows while providing thedynamic pressure cushion. The use of the die of step a) and dynamicpressure cushion eliminates the need for a second die half normallyrequired to form thin sheets of metal. Suitable adhesive materialsinclude, but are not limited to, epoxies, polyesters and applicationspecific adhesives.

Step c:

The laminate 13 is positioned beneath the forming die 6 on asubstantially flat support platen 17. The substantially flat supportedsurface of the laminate 13 defines the reference plane 4. The laminate13 is conditioned by pre-heating the laminate, before or afterpositioning the laminate on the support platen 17, to provide thedynamic pressure cushion and facilitate the process. Note: If anadhesive is chosen that has the appropriate viscosity withoutpre-heating, then preheating is not necessary. The die is pressedagainst the supported conductive foil 8, thereby pressing the conductivefoil 8 into the adhesive 5 to form the conductive foil 8 into thenon-planar pattern (FIG. 5). The appropriate heat and pressure isapplied for the prescribed amount of time to cause the adhesive material5 to flow out from under the circuit features 15 and fill the spaces 16between these to support the circuit features on three sides and producethe structure shown in FIG. 6.

In order to accurately form the conductor the dimensional relationshipbetween the reference plane 4 and the final position of the die 6 isaccurately controlled by the precision die stops 12 contacting thesupport platen 17. It can be appreciated that the dies stops 12 may beprovided on the support platen 17 rather than on the die 6. Moreover,the precision dies stops may be an electronic control, for example, aprecision servo motor. This control is extremely important as itcontrols the shape and location of the conductors 8 as well as the wasteremoval operations. It is critical that the reference plane 4, i.e. thesupported surface of the laminate 13, remains stable and substantiallyflat during forming and waste removal for providing a stable referencepoint for enabling accurate control of the forming and subsequentremoval of the conductor 8 in dimensional relationship to referenceplane 4.

The dimensional relationship of the conductor 8 relative to thereference plane 4 and control of the flow of adhesive 5 under the foilusing the material displacement control grid features 10 on the die arerequired to achieve accurate waste removal. To maintain the dimensionalrelationship between the conductor 8 and the reference plane 4, thematerial expansion troughs 11 are designed to receive the displacedadhesive to avoid material compression that would cause the laminate towrinkle and distort. Thus the expansion troughs 11 ensure that thesupported surface of the laminate 3 remains flush against the supportplate 17, thereby ensuring a stable substantially flat reference plane 4having a natural flatness of ±0.005 mm (0.0002").

The displacement control grid features 10 are designed to ensure thatthe adhesive completely fills all voids so that the conductive sheet 8is continuously supported at, or even lifted and supported at theprescribed level relative to the reference plane 4 for accurate wasteremoval and so that the conductors 15 are supported by the adhesive onthree sides preventing delamination. The displacement control gridfeatures are arranged as a control grid that is dependent on the designof the final circuit configuration, the thickness of the foil, theviscosity and thickness of the adhesive and volume of the adhesive to bedisplaced.

The resulting non-planar pattern is characterized by a set of circuitfeatures 15 that define the finished circuit pattern 3 and raisedportions or ridges 18 of waste material.

Step d:

The die 6 is removed and the laminate 13 (FIGS. 6 and 7) is thensubjected to a precision metal removal process, which mechanicallyremoves, by the use of a diamond fly cutter 52, or other suitablecutting tool, a desired quantity of waste metallic material 18 andadhesive 5 from the exposed metal side of the laminate. The wastematerial is removed down to the dashed machining line 19 (FIGS. 5 and6), which is precisely determined in relation to the reference plane 4at a level sufficient to remove the desired amount of waste material andform the electrically insulated conductive paths 3 depicted in FIGS. 1and 2. The quantity of waste material removed is controlled bycontinuously monitoring the distance between the cutting tool and thereference plane. Machining with a diamond fly cutter produces clean,polished circuits eliminating the need to clean the circuits aftermachining. If not already plated, the conductive paths may then beplated with a desired finish coating (for example, gold, lead, or tin)to complete the conductive network 1. The conductive paths may bespaced, for example, 0.3 mm (0.012 inches) on center.

In some applications, the channeled conductors 3, 3a, 3b may not berequired. For example, in building a flexible printed circuit requiringextreme flexibility, the side walls 3b, despite their thinness, reduceflexibility. Accordingly, in such circumstances waste material removingstep d is continued downward beyond machining line 19 until flushconductors of the desired thickness lacking the side walls 3b have beenachieved. By supporting the conductive paths on three sides they arefirmly entrapped in the adhesive, thereby preventing the paths fromdelaminating during machining. Moreover, flush conductors simplifysubsequent laminating operations and make it possible to pack morecircuit layers in a given thickness.

It will be appreciated that the laminate 13 can be a preformedcommercially available laminate having a suitable adhesive, for example,a thermoplastic adhesive which is heated to allow circuit formation. Thelaminate can also be custom made and may include a fluid orthermosetting adhesive in the Beta-phase (B-stage) during circuitformation. Alternatively, the conductive sheet 8 may be fused (forexample, melted) directly to a flexible dielectric material having thenecessary viscosity fluidity to provide the dynamic pressure cushion orthat is heat treated to provide the necessary viscosity, therebyeliminating the need for a separate adhesive.

Although the circuit forming features 15 in FIGS. 3 and 5 are shown ashaving a trapezoidal cross-section or profile, the die 6 can be designedto provide troughs of any desired open faced cross-sectional shape (forexample, rectangular, hemispherical, ovular, V-shaped, etc).

By quick chilling the laminate as it is being formed or immediatelythereafter, the adhesive and/or dielectric is quickly set up andstabilized. Also, in accordance with the invention, the dielectricmaterial may be rigid rather than flexible, to produce a rigid printedcircuit board having channeled or "flat" conductors.

Although the die 6, support platen 17 and reference plane 4 as describedabove are substantially flat, the die may be a calendar roll and thesupport surface a backing roll. Moreover, although FIG. 7 shows thetrough 20 formed by the displacement control grid feature 10 as beingcompletely machined off, at least a portion thereof may remain aftermachining as shown in FIGS. 11-13.

Embodiment 2: FORMING A CONDUCTIVE MATERIAL OR A LAMINATE INTO A CIRCUITUSING A "TEMPORARY COMPLIANT CARRIER"

A method according to the second embodiment of the invention isillustrated in FIGS. 8-13. In this method the desired circuit patternwith conductors 3 properly positioned in relationship to a referenceplane 14 is produced by the following steps.

Step a:

A forming die 6, as described above with reference to FIG. 3, havingshaped features thereon for forming the conductive sheet 8 (FIG. 4) intoa non-planar pattern defining the final conductive circuits 3, isprovided.

Step b:

(FIG. 8) A laminate 21 of a conductive metal copper foil 8 joined by aflexible dielectric adhesive 2 to a temporary compliant vinyl carrier 22and any desired plating 14 of the foil is provided. The compliantcarrier 22 is applied to the dielectric 2 to provide a substantiallyflat surface defining a reference plane 4 and to support the dielectric2 and the conductive foil 8 and retain the structures dimensions throughsubsequent operations. Moreover, the compliant carrier 22 is selected ortemperature or pressure conditioned (using heat and/or pressure) to havea suitable viscosity to provide the dynamic pressure cushioncharacteristics to receive, capture and support the formed structure.For example, a vinyl carrier may be conditioned by heating to 250° F.,at which temperature it is fluid enough to flow out from under the foil8 but solid enough to support the foil.

In order to maintain dimensional stability of the laminate throughoutthe required circuit forming and finishing (metal removal andlaminating) operations, it is important to establish and maintainreference plane 4. This reference plane 4 accurately defines thelocation of each conductor 3 in relationship to the exposed surface ofthe compliant carrier 22, and is used as the reference for controllingthe removal of waste material and maintaining the desired conductorthickness. Therefore, the substantially flat surface of the temporarycarrier must remain flush against its support surface to maintain astable reference plane.

Step c:

(FIG. 9) The conductive foil 8 is formed into a non-planar pattern bypressing the forming die into the laminate in the same manner asdescribed in step c of Embodiment 1. In this embodiment, however, it isthe flat under surface of the compliant carrier 22, not the dielectric8, that is supported on the support platen 17 to provide the referenceplane 4.

Step d:

(FIGS. 10 and 11) The waste material is now mechanically removed, by theuse of a diamond fly cutter, down to machining line 23, which isprecisely determined in relation to reference plane 24, in the samemanner as described in step d of Embodiment 1, leaving conductive paths3 (FIG. 11). Note that, unlike Embodiment 1, a portion 20 of thesections of the conductive foil 8 that were depressed by the flowcontrol grid features 10 remain after waste material removal (FIG. 11).These do not, however, form a part of the conductive network beingmanufactured.

Step e:

(FIG. 12) A layer of dielectric, with a layer of adhesive thereon, isnow applied to the machined surface to support and protect theconductive paths. This layer of dielectric is applied such that theadhesive completely fills all voids between the dielectric and themachined surface.

The (FIG. 13) compliant carrier 22 is heated and removed after thecircuit is complete. (FIG. 13).

The compliant carrier 22 may be attached to the dielectric 2 prior to orsimultaneously with forming of the foil 8. Furthermore, the foil 8 maybe custom attached to the dielectric 2 or it may be purchased on themarket as a preformed laminate. Moreover, the compliant carrier 36 maybe attached directly to the conductive sheet 22 with or withoutadhesive.

As in Embodiment 1, in order to stabilize the structure it may bequickly chilled thereby setting-up and stabilizing the compliant carriersubsequent to or during forming. The compliant carrier is heated forremoval subsequent to this chilling and the attachment of dielectriclayer 2.

In embodiments 3, 4 and 5 of the invention described hereinafter, theconductive material (e.g. copper) itself provides the dynamic pressurecushion and a first reference plane for controlling the waste removalprocess. FIGS. 14 through 16 illustrate a circuit having flat conductors25, sculptured bi-thickness conductors 26 and raised terminal pads andregistration posts 27 that will be used below to describe theseembodiments.

As shown in FIGS. 14-16 a dielectric layer 28 is adhered to the formedconductive material 29, using a layer of adhesive 30. In one embodimentthe dielectric layer 2 is provided with pre-punched alignment holes 31that are received over the registration posts 27 (FIG. 16) to accuratelyalign the dielectric 2 with the conductors. In other embodiments thedielectric layer 2 is not prepunched and the registration posts are usedto raise the dielectric to a level sufficient to allow the dielectricand adhesive overlying the registration posts to be removed during theremoval step. FIG. 14 shows the circuit with the dielectric omitted sothat the circuits are visible.

It will be appreciated that the conductive material in these embodimentsmay itself be a laminate, for example, copper fast with a substrate ofaluminum.

Embodiment 3: FORMING A CONDUCTIVE SHEET INTO A CIRCUIT BY EXTRUDING THECONDUCTIVE SHEET AND ATTACHING A "TEMPORARY COMPLIANT CARRIER".

According to Embodiment 3, a supported conductive circuit with theconductors 25, 26 properly positioned in relationship to a referenceplane 32 is formed by the following steps described with reference toFIGS. 17-22.

Step a:

A forming die 6, similar to that described in step a of embodiment 1with reference to FIG. 3, for forming a solid layer of conductivematerial 29 into a non-planar pattern defining the final conductivecircuits 3, is provided.

Step b:

A solid sheet of copper 29 having substantially planar surfaces, one ofwhich is supported on a support platen and defines the first referenceplane 32, is provided (FIG. 17). Thus, the need to attach a separatesubstrate, for example, a dielectric or temporary carrier, to define thereference plane is eliminated. This "reference plane" 32 is critical toproper waste removal and conductor shaping (thickness, width andconfiguration).

Step c:

(FIG. 17) The conductive material 32 is extruded, by pressing theforming die 6 into the conductive material against a planar supportplaten in contact with the first reference plane 32, thereby forming anon-planar pattern defining the desired conductive features 25, 26, 27.By strictly controlling the extrusion process relative to the firstreference plane 32 using die stops as described in Embodiment 1, therequired control dimensions are held within a tolerance of ±0.0025 mm(0.0001") measured from the conductor's surface to the first referenceplane 32. (FIG. 17)

The forming step is said to extrude the conductive material because whenthe forming die 6 is pressed into the conductive material 29, thematerial flows out from under the circuit forming features 9 and isextruded up into the terminal pad recesses and into the recessed circuitforming elements, thereby extruding the terminal pads 27 and thecircuits 25, 26 up into the forming die.

Terminal pads 27 are also raised registration posts that are used toaccurately align and lock the dielectric in place throughout themachining process. The posts and pads could, however, be separatefeatures.

Step d:

(FIGS. 18 and 19) A pre-punched dielectric layer 28, having adhesivelayer 30, also dielectric, thereon, is applied over the extrudedconductive material 27, 25, 26, the adhesive 30 being sufficiently fluidto completely fill all the spaces between the conductors 25, 26 andbetween the conductors and the dielectric layer 28. (FIG. 19) Thedielectric layer is accurately positioned over the extruded circuitpattern 25, 26 by passing prepunched openings 31 over the registrationposts/contact pads 27. (FIG. 19) Any desired surface finish (not shown)may be plated onto the exposed circuit features using base 29 as acommon plating buss.

Step e:

(FIG. 20) A temporary, "compliant carrier" 33 is now applied over thedielectric 28 to support and protect the uninsulated conductor pads 27throughout the subsequent machining operation. The "compliant material"33 (e.g. a low temperature vinyl) is heated and applied over thedielectric 28 using a conventional roll laminating process. This processprecisely applies the material 33 over the dielectric 28, filling-in alllow spots and establishing a second reference plane 34 in precisedimensional parallel relation to the first reference plane 32. Thesecond reference plane 34 is defined by the surface of the compliantcarrier 33 opposite the extruded conductor material 29 (FIG. 20).

Step f:

(FIGS. 20, 21) The waste material is removed, using a diamond flycutter, from the extruded conductive material 29 up to machining line 31using the "second" reference plane 34 to control the removal ofconductive material and define the final shape and thickness of thefinished conductor. Hence, the first reference plane 32 here serves onlyas an intermediary for controlling the forming step and application ofthe second reference plane 34.

Step g:

(FIG. 22) Finally the temporary compliant carrier 33 is removed (byheating and peeling) leaving the finished supported conductive circuit.

The steps of attaching the dielectric 28 and attaching the "compliantcarrier" 33 may be performed simultaneously. It can also be appreciatedthat the compliant carrier may be left in place for supporting andprotecting the circuit.

Embodiment 4: FORMING A CONDUCTIVE SHEET INTO A CIRCUIT BY EXTRUDING ACONDUCTIVE SHEET TO FORM RAISED FEATURES AND COVERING THESE WITH A LAYEROF UNPUNCHED DIELECTRIC MATERIAL

This embodiment according to the invention, described with reference toFIGS. 23-27, eliminates the technical and cost limitations related topreparing and applying the pre-punched dielectric layer of the previousprocess and provides low cost removal of dielectric from the terminalpads 27 by providing the following steps.

Steps a, b and c:

A die (step a) and a solid sheet of copper 29 (step b) are provided asin steps a, and b of embodiment 3. The conductive material is extrudedinto a non-planar pattern (step c) defining circuit elements 27, 25, 26on one face thereof in relation to a first reference plane 32 supportedon a planar support platen as described in step c of embodiment 3. (FIG.23)

Step d:

(FIGS. 24 and 25) A dielectric layer 35, without the prepunched openings31 disclosed in embodiment 3, having an adhesive layer 36 thereon isapplied to the circuit feature defining face of extruded conductivesheet 29 (FIG. 25) filling all voids as described in step d ofembodiment 3 and covering all of the circuit features 27, 25, 26.

Step e:

(FIG. 26) The raised portions of the dielectric 35 are preciselymechanically removed down to machining line 37, determined in strictdimensional relation to the first reference plane 32, thereby exposingterminal pads 38 of circuits 26. The machining removes the tops of theterminal pads 27 to form exposed pad areas 38 that are flush with theexposed surface of the dielectric 35 (FIG. 26). If desired the exposedcircuit features may be appropriately plated (not shown).

The dielectric 35 is precisely removed relative to the first referenceplane 32 using a high speed diamond fly-cutter, such that the resultingsurface is substantially planar and defines a second reference plane 39parallel and accurately located relative to the first reference plane.

Step f:

The waste material is now removed from the extruded conductive material29 up to machining line 40 using the second reference plane 39 tocontrol the removal of conductive material 29 and define the final shapeand thickness of the finished conductors 25, 26 leaving the finalcircuit pattern (FIG. 27).

Advantages of the fourth embodiment over the third embodiment are a)reduced Labor, due to reduced material preparation (no drilling orpunching of through holes), and handling (no need to alignment holeswith terminal pads), b) flush terminal pads offer a significantadvantage to those manufacturers choosing to attach surface mountedcomponents.

Embodiment 5: FORMING A CONDUCTIVE MATERIAL INTO A CIRCUIT BY EXTRUDINGTHE CONDUCTIVE MATERIAL AND MACHINING THE EXTRUDED CONDUCTIVE MATERIALON BOTH SIDES

Machining the conductive circuits on both sides according to this methodof the invention enables the production of ultra thin fine line circuitswith (e.g. 0.013 mm (0.0005") thick) conductors. It also produces aconductor that is flat on both surfaces and that has a uniform thicknessregardless of the conductor width, using an inexpensive, inconsistent,etched template. In this approach, as in the previous embodiment, areference plane 32 is utilized. A conductive circuit is formed accordingto embodiment five described with referenced to FIGS. 28-34 as follows.

Steps a, b and c:

A die (step a) and a solid sheet of copper 29 (step b) are provided asin steps a, and b of embodiment 3. However, a cheap etched die isprovided in this embodiment. The conductive material is extruded into anon-planar pattern (step c) defining circuit elements 25, 26 relative toa first reference plane 32 that is supported on a planar support platenas described in step c of embodiment 3. The resulting conductors havediffering thickness, due to the low cost etched die (template), (FIG.28).

Step d:

(FIGS. 28 and 29) Waste material is removed down to machining line 41based on the first reference plane 32, leveling all the conductors 25,26 to a uniform thickness relative to the first reference plane 32 (FIG.29). In this embodiment, control dimensions are measured from the flatbase of the formed conductor, i.e. the reference plane 32, to theexposed machined surface of the conductors 25, 26 which are formedwithin a tolerance of ±0.0025 mm (0.0001").

Step e:

(FIG. 30) A dielectric layer 42 having a layer of adhesive 43 thereon,is precisely applied to the formed machined conductors 25, 26establishing a second reference plane 44 parallel to and accuratelypositioned relative to the first reference plane 32. The dielectriclayer 42 is applied such that the adhesive 43 fills all voids betweenthe conductors 25, 26 and between the conductors and the dielectric 42.

Step f:

(FIG. 31) Using the second reference plane 44, the waste material isprecisely removed up to the machining line 45 reducing the conductors totheir final thickness and in so doing defining the finished circuitpattern to an accuracy of 0.0025 mm (0.0001") due to the accuratecontrol resulting from the use of the reference planes 32, 44.

Step g:

(FIGS. 32 and 33) If a second insulating dielectric is required it iseasily laminated in place as the conductors 25, 26 are flush with theadhesive (FIG. 32) and there are no raised conductors to emboss over.The fact that a dielectric is not being embossed over conventionalconductors also greatly improves the circuit's dimensional stability.The conductive material may be heat treated to reestablish the desiredmetal temper as necessary. Moreover, in applying the second dielectric,the residual (stored) heat may be used to fuse the dielectric(s) to theformed metal. (FIG. 33)

An example of a circuit with features formed by a die having a controlgrid according to the invention is shown in FIG. 34 in which the wastematerial has been removed from the laminate on the right side of lineA--A, but not on the left side of line A--A. Control grid features inFIG. 34 partially remain after machining and can be seen as rows ofsmall squares located in the areas between the circuit paths.

The control grid must be designed to control the flow of the adhesive orthe dielectric substrate during forming such that the conductivematerial is deformed into two, three or more levels, i.e. the wastematerial level, and various circuit levels, in planar configurations.The control grid must also control the flow of the adhesive ordielectric so that the various levels are supported on three sides bythe adhesive or dielectric without any voids being created. All of thismust be done while maintaining a flat reference surface in strictdimensional relation with the various material levels.

The control grid and expansion troughs must also control the flow of theadhesive or dielectric such that the adhesive or dielectric is displacedand not compressed. The expansion troughs allow the adhesive ordielectric to be displaced upwards into the die relieving anycompression stresses that would distort the formed structure. Thus thesupported surface of laminate remains flush against the support platen17 providing a stable, flat reference plane, which the known methods areunable to produce.

When the forming die is a cylindrical forming roll and the conductor isformed by feeding the conductor between the forming roll and a supportsurface, the control grid helps keep the dielectric or adhesive fromflowing to either side, relative to the direction of travel of theconductor. The control grid thus helps ensure that the flow of adhesiveor dielectric is uniform across the width of the conductor as it is fedbetween the forming roll and the support surface, thereby providingtransverse dimensional uniformity in the formed non-planar pattern.

The design of the control grid is dependent on the geometry of the finalcircuit to be formed, the thickness of the adhesive or dielectric layerand the volume of the adhesive or dielectric to be displaced duringforming. The volume of adhesive or dielectric to be displaced iscalculated from the length, width, thickness and spacing of theconductors to be formed. From this information, the width, length,thickness and location of the forming die's displacing features,including displacement grid, and/or expansion troughs can be determined.

Because each circuit configuration is different, there is no set formulafor designing the forming die. Each forming die must be designed toachieve the desired result based on the material characteristics andconfiguration of the circuit to be formed.

In order to precisely control the depth of cutting during waste removal,the forming die may also include one or more machining depth of cutindicator forming elements 51 (FIG. 3) for forming machining depth ofcut indicators in the conductor. The depth of cut indicator formingelements 51 are sized to form the cut indicators such that the unexposed(lower) surface of the indicator is at a level relative to the referenceplane that is at the same level as, or just above, the exposed surfaceof the conductors. Subsequently, as the waste material is being removedthe machining depth of cut indicator is optically or electricallymonitored. In one arrangement, when the indicator is removed itindicates that the proper depth of cut has been achieved and cutting iscontrolled at that depth thereby ensuring precise control of cuttingdepth.

It is noted from the foregoing that the process of this invention allowsthe production of fine-line flexible conductive networks (for example,circuits and jumpers) and conventional, high volume, printed circuitboards at relatively low cost through an environmentally desirableprocess.

As will be appreciated, the process of the present invention is veryversatile and permits the creation of a conductive pattern in one ormore of the various embodiments herein described.

The present invention also permits the production of sculptured (3dimensional) circuit networks in which portions of the network arethicker than others thereby to provide, for example, rigid contact areaswith flexible interconnects. This is accomplished by creating theappropriate three dimensional forming die which includes the desiredfeatures, for example see FIGS. 14-16, utilizing a conductive materialor composite material laminate, which is then formed as hereinbeforedescribed.

Conductor networks and/or their terminating points, in accordance withthe present invention, may be plated with any surface finish because thepresent invention has the ability to manufacture conductor networks froma sheet or roll of conductive material on which a suitable contactfinish (for example, gold) has been previously placed or inlaid. Thisapproach is only practical with the process of the present invention asthe process mechanically defines each conductor by grinding off unwantedwaste material between each conductor thereby easily removing anyunwanted gold. This contrasts sharply with conventional etching systemsused to create printed circuit boards as conventional etching solutionswill not remove gold and therefore would require additional processingsteps. Consequently, the present invention significantly reduces bothcosts of applying and selectively removing the desired contact finish.

The final conductive paths and their terminating points can be designedto any specific electrical parameter (for example, power and signal) orconfiguration. For example, the controlled impedance of each conductivepath can be selected to suit a particular application by appropriatelycontrolling its configuration and/or its relationship to an electricallyconductive support structure (for example, a spring layer or shield) ifany. It is important to note that although conductors and/or theirterminating points can be plated with any surface finish, if a conductorpattern is not electrically connected to a common plating bus, the gold,by example, must be plated on before the conductive paths areelectrically isolated.

Further, depending on the use of the conductive network, the conductivepaths can be insulated with a pre-windowed protective overlay or soldermask. Suitable insulating materials include but are not limited to,Kapton, Mylar and Teflon. This protective overlay provides a means toconstruct multi-layer conductive networks (for example, multi-layercircuit boards) or to add shielding material to the conductive network.

In embodiments in which the dielectric material is adhesively attachedto the copper, the circuit pattern may be formed in the copper layerwith the dielectric material undeformed. Here the adhesive is displacedto allow the pattern formation and to fill the voids otherwise produced.The conductive network can be insulated with a protective overlay, ifrequired, and may be used to produce multi-layer circuit boardsoverlaying one another with appropriate protective intermediatedielectric material insulating the boards except where contact isdesired through openings or windows.

Pressure fused interconnections can be easily created to join twoconductive sheets, one of which has stress hardened domes located at thepoints to be interconnected, using high pressure rollers. This isaccomplished with the two sheets of conductive networks registered toeach side of a prepunched windowed flexible dielectric layer. Theflexible dielectric material, for example, 0.055 mm (0.002 inches)thick, may be polyester. The stress hardened domes produce pressurefused interconnections as they pass through the high pressure rollers.In additional each interconnect is structurally reinforced by thelaminating process.

The laminate provided in the first and second embodiments may comprisetwo or more conductive layers, i.e. sheets 53, 54 of copper or otherconductive metallic material, connected by an intermediate layer(s) ofdielectric or adhesive 55 (FIG. 35). During forming (FIG. 36) bothconductive layers may be formed at the same time such that a pluralityof layers of conductive paths remain after a single waste removalprocess. (FIG. 37)

Two different conductive networks may be formed on opposite sides of thelaminate shown in FIG. 35 by providing a first compliant carrier 56defining a first reference plane, deforming the first conductive layer53 in a first forming step, and leaving a first network of conductivepaths in a first waste removal step. Next, a dielectric or a secondtemporary compliant carrier is applied to the machined surface providinga second reference plane and the first carrier is removed. A secondnetwork of conductive paths is now produced by forming the secondconductive layer 54 in a second forming step and removing waste materialin a second waste removal step.

In an alternative embodiment the laminate or conductive sheet or layerof all the disclosed embodiments is provided as a continuous sheet ofmaterial supplied on a roll, and the forming die is a forming roller. Inthis embodiment the continuous sheet is fed between the forming rollerand a support surface, after any desired temporary compliant carrieretc. is applied, forming the sheet into the non-planar pattern. Thewaste removal and any other desired procedures are performed on thesheet, i.e. application of a dielectric, and the continuous sheet havingthe desired conductive paths formed therein is wound onto a receivingroll. In this manner the formed circuits may be stored as a roll ofcircuits that are conveniently unrolled and cut from the continuoussheet as desired. The roll of circuits also provides an advantageous,compact package of circuits for storage and shipment.

By utilizing a forming roller having a control grid, expansion troughsand precision die stops, as disclosed above, the present inventioncontrols the flatness of the formed circuit, relative to the referenceplane, to within 0.005 mm (0.0002") across a 30.5 cm (12"), minimum,wide roll of material that is typically 635 cm (250") long.

We claim:
 1. A method for manufacturing a network of electricallyconductive paths supported by a dielectric material comprising the stepsof:a) providing a lamina having at least two sheets of metallic materialconnected and electrically insulated from each other by an intermediatelayer of dielectric material; b) supporting the lamina on a firstsurface thereof; c) defining a reference plane positioned parallel tothe lamina; d) mechanically forming the lamina into a non-planar patterndefining the network of conductive paths substantially parallel to thereference plane; and e) machining the lamina, parallel to the referenceplane, along a boundary between waste material of the lamina and thenetwork of conductive paths, to remove the waste material and leave thenetwork of conductive paths;wherein a layer of dielectric material ismade fast with the lamina, before step e), such that the conductivepaths are supported throughout performance of a remainder of the method.2. A method according to claim 1, wherein all the metallic sheets areformed simultaneously in step d) and the waste material from all thesheets is removed simultaneously in step e).
 3. A method according toclaim 1, wherein there are two conductive sheets attached together by anintermediate layer of adhesive, and further comprising;applying a firsttemporary compliant carrier to an exposed surface of a first of saidsheets, an exposed surface of the first carrier defining a firstreference plane; forming the first sheet into a first non-planar patterndefining a first network of conductive paths parallel to said firstreference plan; removing waste material from the first sheet along aboundary between waste material and the conductive paths, leaving thenetwork of conductive paths; applying a second temporary compliantcarrier to an exposed surface of a second of said sheets, an exposedsurface of the second carrier defining a second reference plane; formingthe second sheet into a second non-planar pattern defining a secondnetwork of conductive paths parallel to the second reference plane;removing waste material from the second sheet along a boundary betweenwaste material and the conductive paths, leaving the second conductivenetwork of conductive paths.
 4. A method according to claim 1, whereinsaid lamina is thin.
 5. A method for manufacturing a network ofelectrically conductive paths supported by a dielectric materialcomprising the steps of:a) providing a conductive metallic lamina; b)making a dielectric substrate fast with the lamina, such that an exposedsurface of the substrate defines a reference plane disposed parallel tothe lamina; c) supporting the substrate on the exposed surface thereof;d) mechanically deforming the lamina into a non-planar pattern definingthe network of conductive paths substantially parallel to the referenceplane, contiguous and integral with areas of waste conductive material,and defining a machining plane parallel to the reference plane along aboundary between waste material of the lamina and the network ofconductive paths; e) machining the lamina along the machining plane toremove the waste material and leave the network of conductive paths; andf) providing at least a portion of the substrate, adjacent the lamina,with a viscosity during step d) such that the substrate is sufficientlyfluid to flow from under the conductive paths being formed to relieveany compression stresses and to fill voids under waste material of thelamina, and is sufficiently viscous to support the lamina during andafter formation.
 6. A method according to claim 5 wherein the substrateis a laminate comprising a dielectric lamina and a dielectric adhesivelayer, the adhesive providing the desired viscosity during step d).
 7. Amethod according to claim 5, wherein the substrate is a temporarycompliant carrier fast with the first surface of the lamina.
 8. A methodaccording to claim 7 comprising the step of making fast a dielectriclamina to the network of conductive paths on a side of the paths remotefrom the temporary compliant carrier after step e) with the dielectriclamina filling any voids between the network of conductive paths andbetween the dielectric lamina and the metallic lamina, and then removingthe temporary compliant carrier.
 9. A method according to claim 5,wherein said forming step comprises depressing portions of the lamina,relative to the reference plane, into the substrate to form recessedchannels in the lamina defining the desired conductive paths whileleaving the waste metallic material of the lamina undepressed;depressingsections of the undepressed waste regions of the lamina into thesubstrate, said sections defining a flow control grid located anddimensioned to control the flow of the substrate during the forming stepd) to ensure that the substrate flows under the lamina as the lamina isbeing formed, such that the substrate fills any voids, relieves anycompression stresses and supports the lamina during and after formingwith the network of conductive paths positioned as desired parallel withthe reference plane.
 10. A method according to claim 5, comprisingproviding a forming die having a forming surface for forming the laminainto said non-planar pattern defining a network of electricallyconductive paths, the forming surface having thereon:conductive pathforming elements sized, shaped and arranged to define the network ofconductive paths; flow control grid elements sized, shaped and arrangedfor depressing a second surface of the lamina to control the flow ofsubstrate material during the forming step d) to ensure that thesubstrate material flows, as the sheet is being formed, to relievecompression stresses and to fill any voids created during forming, andto ensure that the lamina is supported at desired levels during forming.11. A method according to claim 10, wherein the width, thickness, shapeand arrangement of the flow control grid features are based upon thematerial forming the substrate, the thickness and volume of thesubstrate material to be displaced during forming, for controlling theflow of the substrate material during forming.
 12. A method according toclaim 10, comprising supporting the first surface of the lamina on asupport platen defining the reference plane; andproviding the die withprecision die stops for contacting the support platen to control theforming operation relative to the reference plane.
 13. A methodaccording to claim 10, comprising providing the forming die withmaterial expansion troughs recessed in the forming surface for allowingportions of the lamina to be pressed up by the substrate during theforming step d) for relieving compression stresses that would otherwisebe created.
 14. A method according to claim 5, wherein step e) isperformed with a diamond fly cutter.
 15. A method according to claim 5,wherein step a) comprises, providing a continuous lamina on a roll;andcollecting the lamina, after step e), on a receiving roll.
 16. Amethod for manufacturing a network of electrically conductive pathssupported by a dielectric material comprising the steps of:a) providinga conductive metallic lamina; b) supporting the lamina on a firstsurface thereof, such that the supported surface of the lamina defines afirst reference plane; c) mechanically deforming a second surface of thelamina, substantially parallel with the first surface reference plane,by depressing the waste portions of the lamina toward the firstreference plane while extruding the desired network of conductive pathsin a direction away from the first reference plane, and defining amachining plane substantially parallel to the first reference planealong a boundary between waste material of the lamina and the extrudednetwork of conductive paths; d) making a layer of dielectric materialfast with the formed second surface of the lamina, such that an exposedsurface of the dielectric layer defines a second reference planedisposed substantially parallel to the first reference plane, and theconductive paths are supported throughout performance of a remainder ofthe method; e) supporting the exposed surface of the dielectricmaterial; and f) machining the first surface of the lamina, relative tothe second reference plane, along the boundary, thereby removing thewaste material and leaving the desired conductive paths.
 17. A methodaccording to claim 16, wherein step d) comprises, providing thedielectric layer with a layer of dielectric adhesive to attach the layerto the second surface, and applying the dielectric layer to the formedsecond surface of the lamina with the adhesive filling all voids betweenthe desired conductive paths and between the lamina and the dielectriclayer.
 18. A method according to claim 17 wherein step f) leaves thedesired electrically conductive paths flush with the adhesive fillingthe voids therebetween, whereby the conductive paths are support onthree sides thereof by the layer of dielectric material.
 19. A methodaccording to claim 16, comprising machining the formed second surface ofthe lamina, parallel to the first reference plane, to machine theextruded conductive paths all to the same level parallel to the firstreference plane before step e).
 20. A method according to claim 19,wherein step d) comprises, providing the dielectric layer with a layerof dielectric adhesive to attach the layer to the second surface, andapplying the dielectric layer to the formed and machined second surfaceof the lamina with the adhesive filling all voids between the desiredconductive paths and between the lamina and the dielectric layer.
 21. Amethod according to claim 20, wherein step f) leaves the conductivepaths flush with the adhesive filling the voids therebetween, to supportthe conductive paths on three sides thereof by the layer of dielectricmaterial.
 22. A method according to claim 16, comprising making a sheetof dielectric material fast with the machined first surface of thelamina.
 23. A method for manufacturing a network of electricallyconductive paths supported by a dielectric material comprising the stepsof:a) providing a conductive metallic lamina; b) supporting the laminaon a first surface thereof; c) defining a first reference planepositioned parallel to the lamina; d) mechanically deforming a secondsurface of the lamina into a non-planar pattern defining the network ofconductive paths substantially parallel to the first reference plane,contiguous and integral with areas of waste conductive material, anddefining a machining plane substantially parallel to the first referenceplane along a boundary between waste material of the lamina and thenetwork of conductive paths, by extruding the desired conductive pathsto at least a first level, relative to the first reference plane, andextruding raised terminal pad portions that are raised outwardly fromthe at a least first level, relative to the first reference plane: e)making a layer of dielectric material fast to the formed second surfaceof the lamina, such that conductive paths are supported throughoutperformance of a remainder of the method; and f) machining the laminaalong the machining plane to remove the waste material and leave thenetwork of conductive paths.
 24. A method according to claim 23,comprising, providing the layer of dielectric material with pre-punchedalignment holes for receiving the raised terminal pads; andmaking fastthe layer of dielectric material to the formed second surface, with theraised terminal pads engaging and extending through the pre-punchedalignment holes.
 25. A method according to claim 24, wherein the step ofmaking fast the pre-punched dielectric sheet comprises, providing thepre-punched dielectric with a layer of pre-punched dielectric adhesive,and applying the pre-punched dielectric to the formed second surface ofthe lamina such that the adhesive fills all voids between the desiredconductive paths and between the lamina and the dielectric layer;thestep of machining comprises machining the first surface of the lamina toleave the desired electrically conductive paths flush with the adhesivefilling the voids therebetween.
 26. A method according to claim 24,comprising making fast a temporary carrier to an exposed surface of thepre-punched dielectric to provide a second reference plane parallel tothe first reference plane;machining the first surface of the lamina,relative to the second reference plane, along the boundary, therebyremoving the waste material and leaving the desired conductive pathsfinished to a desired thickness.
 27. A method according to claim 23,comprising making fast the dielectric layer to the formed second surfaceof the lamina, such that portions of the dielectric layer overly theraised terminal pads; andprecisely machining an exposed surface of thedielectric layer, parallel to the first reference plane, to remove theraised portions of the dielectric layer and removing tops of the raisedterminal pad portions to provide exposed terminal pads that are flushwith the exposed surface of the dielectric layer, the machined exposedsurface of the dielectric layer defining a second reference planeparallel to the first reference plane.
 28. A method according to claim27, comprising supporting the machined second surface of the lamina andmachining the first surface of the lamina, parallel to the secondreference plane, along the boundary, thereby removing the waste materialand leaving the desired conductive paths finished to the desiredthickness.
 29. A method according to claim 27, wherein the step ofmaking fast the dielectric layer comprises, providing the dielectriclayer with a layer of dielectric adhesive and applying the dielectriclayer to the formed second surface of the lamina such that the adhesivefills all voids between the desired conductive paths and between thelamina and the dielectric layer; andthe step of machining comprisesmachining the first surface of the lamina to leave the desiredelectrically conductive paths flush with the adhesive filling the voidstherebetween.
 30. A method according to claim 23, wherein step d)comprises, extruding the conductive paths to different levels, relativeto the first reference plane, representing various conductor paththicknesses, relative to the first reference plane.